JP2018188581A - Active ray curable inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an active ray curable inkjet ink that makes it possible to obtain an image having all of flexibility, adhesion to recording medium and scratch resistance.SOLUTION: An active ray curable inkjet ink contains a polyfunctional (meth) acrylate compound, a polyfunctional vinyl ether compound, and a fluorescent brightener, where the content of the polyfunctional (meth) acrylate compound is 60 mass% or more and the polyfunctional (meth) acrylate compound contains a hydrophobic polyfunctional (meth) acrylate compound.SELECTED DRAWING: None

Description

  The present invention relates to an actinic ray curable inkjet ink.

  The ink jet recording method is used in various printing fields because it can form an image easily and inexpensively. As a kind of inkjet ink, an ink that is cured by being irradiated with actinic rays is known. In the case of forming an image using actinic ray curable ink, the ink droplets are landed on the surface of the recording medium, and the landed droplets are irradiated with actinic rays. As a result, the actinic ray polymerizable compound in the droplets is polymerized, and a cured product (image) is formed on the surface of the recording medium. According to the image forming method using actinic ray curable ink, there is an advantage that an image having high adhesion can be formed regardless of the water absorption of the recording medium.

  As such actinic ray curable ink-jet ink, for example, an ink containing a (meth) acrylate compound, a vinyl ether compound, and a radical polymerization initiator has been proposed (Patent Document 1). On the other hand, an actinic ray curable inkjet ink containing a radical polymerizable compound such as a (meth) acrylate compound, a radical polymerization initiator, and a fluorescent brightening agent has also been proposed (Patent Document 2). Furthermore, a coating varnish containing a radical polymerizable compound such as amine-modified (meth) acrylate, a radical polymerization initiator, and a fluorescent brightening agent has also been proposed.

JP2015-160890A JP 2012-31254 A JP 2011-213965 A

  The ink containing the vinyl ether compound described in Patent Document 1 has an advantage that a cured product having high flexibility can be obtained. However, the cured product obtained from the ink had low adhesion to the recording medium and further low abrasion resistance. The reason is considered as follows. When a (meth) acrylate compound and a vinyl ether compound are polymerized, a structure derived from vinyl ether is introduced between polymer chains derived from (meth) acrylate due to the difference in the polymerization ratio. Therefore, compared with the case where only a (meth) acrylate type compound is polymerized, a crosslinking density becomes low. That is, while the flexibility of the cured product is increased, the abrasion resistance and the like are decreased. Further, when the crosslink density of the cured product is lowered, the adhesion between the cured product and the recording medium tends to be easily lowered. The reason is considered to be that the film becomes soft, so that the film is easily broken during a tape peeling test or the like, and the adhesiveness is lowered.

  On the other hand, in the ink or coating varnish containing the fluorescent whitening agent described in Patent Literature 2 and Patent Literature 3, the fluorescent whitening agent interacts with a radical polymerization initiator and the like, and radical generation efficiency and the like increase. As a result, the crosslinking density of the radical polymerizable compound is increased, and the adhesion between the cured product and the recording medium is increased. However, there is a problem that the cured film is likely to be excessively hard and is difficult to apply to uses that require flexibility.

  The present invention has been made in view of the above problems. Specifically, the present invention provides an actinic ray curable inkjet ink capable of obtaining an image having flexibility, adhesion to a recording medium, and abrasion resistance.

The present invention relates to the following actinic ray curable inkjet ink.
[1] A polyfunctional (meth) acrylate compound, a polyfunctional vinyl ether compound, and a fluorescent brightening agent, wherein the content of the polyfunctional (meth) acrylate compound is 60% by mass or more, The (meth) acrylate compound is an actinic ray-curable inkjet ink containing a hydrophobic polyfunctional (meth) acrylate compound.

[2] The actinic ray-curable inkjet ink according to [1], wherein the polyfunctional vinyl ether compound is an ethylene oxide modified product.
[3] The actinic ray-curable inkjet ink according to [1] or [2], further comprising an amine-modified (meth) acrylate oligomer.
[4] The actinic ray-curable inkjet ink according to any one of [1] to [3], further including a radical polymerization initiator.
[5] The radical polymerization initiator includes an intramolecular bond cleavage radical polymerization initiator, and the content of the intramolecular bond cleavage radical polymerization initiator is 0.1 to 3.5% by mass. 4]. The actinic ray-curable inkjet ink according to item 4.

[6] The actinic ray-curable inkjet ink according to any one of [1] to [5], further containing an antioxidant.
[7] The actinic ray-curable inkjet ink according to any one of [1] to [6], further including a color material.
[8] At least one gelling agent selected from the group consisting of an aliphatic ketone, an aliphatic ester, a higher fatty acid, a higher alcohol, and an amide compound having a linear or branched hydrocarbon chain having 14 or more carbon atoms. The actinic ray-curable inkjet ink according to any one of [1] to [7], containing 5 to 10% by mass.

  According to the actinic ray curable inkjet ink of the present invention, it is possible to obtain an image having flexibility, adhesion to a recording medium, and abrasion resistance.

  The actinic ray curable inkjet ink of the present invention (hereinafter also simply referred to as “ink”) includes a polyfunctional (meth) acrylate compound (mainly a hydrophobic polyfunctional (meth) acrylate compound) and a polyfunctional vinyl ether compound. And a brightening agent, and is cured by irradiation with actinic rays. Here, the actinic rays are electron beams, ultraviolet rays, α rays, γ rays, X-rays, etc., preferably ultraviolet rays and electron beams. The ink of the present invention may contain components other than those described above as necessary. For example, radical polymerization initiators, amine-modified (meth) acrylate oligomers, antioxidants, coloring materials, gelling agents, polymerizations other than those described above. May further contain an ionic compound or the like. Here, the description of (meth) acrylate in this specification includes one or both of acrylate and methacrylate. Similarly, the “(meth) acryloyl group” includes one or both of an acryloyl group and a methacryloyl group.

  In conventional actinic radiation curable ink-jet inks, when trying to increase the flexibility of a cured product, the adhesion and scratch resistance with a recording medium tend to be low, while the adhesion and scratch resistance with a recording medium are reduced. When it raises, the subject that the softness | flexibility of hardened | cured material became low occurred. That is, the flexibility of the cured product, the adhesion to the recording medium, and the abrasion resistance are in a trade-off relationship, and it is difficult to provide them at the same time.

On the other hand, when the present inventors diligently studied, by using an ink containing a hydrophobic polyfunctional (meth) acrylate compound, a polyfunctional vinyl ether compound, and a fluorescent brightening agent, flexibility, a recording medium It was found that an image having both adhesiveness and abrasion resistance can be obtained. As described above, when a hydrophobic polyfunctional (meth) acrylate compound and a polyfunctional vinyl ether compound are polymerized, a structure derived from a vinyl ether compound is introduced between polymer chains derived from the hydrophobic polyfunctional acrylate compound. The Both the vinyl ether compound and the hydrophobic polyfunctional (meth) acrylate compound have a structure that easily undergoes a chain transfer reaction. It has been found that when a brightening agent is added to such a system, the brightening agent functions as a chain transfer agent. That is, in the ink of the present invention, a chain transfer reaction occurs during the curing, and the crosslink density of the cured product is sufficiently increased. At this time, it was also found that the crosslink density of the cured product is sufficiently increased by setting the amount of the polyfunctional (meth) acrylate compound to 60% by mass or more based on the total amount of the ink. On the other hand, when the structure derived from the vinyl ether compound is included between the structures derived from the hydrophobic polyfunctional (meth) acrylate compound, the crosslink density is hardly excessively increased and the flexibility of the cured product is improved. Therefore, according to the ink of the present invention, a cured product having both flexibility, adhesion to the recording medium, and abrasion resistance can be obtained.
Hereinafter, components contained in the ink of the present invention will be described.

1. Polyfunctional (meth) acrylate compound The ink of the present invention contains 60% by mass or more of a polyfunctional (meth) acrylate compound with respect to the total amount of the ink. The polyfunctional (meth) acrylate compound may be a compound having two or more (meth) acryloyl groups in the molecule, but is preferably a hydrophobic polyfunctional (meth) acrylate compound. The amount of the hydrophobic polyfunctional (meth) acrylate compound relative to the total amount of the polyfunctional (meth) acrylate compound is preferably 65% by mass or more, more preferably 80% by mass or more, and polyfunctional (meth). It is particularly preferable that all of the acrylate compounds are hydrophobic polyfunctional (meth) acrylate compounds. The polyfunctional (meth) acrylate compound does not include a polyfunctional vinyl ether compound described later.

  The hydrophobic polyfunctional (meth) acrylate compound is not particularly limited as long as it has two or more (meth) acryloyl groups in the molecule and is a hydrophobic compound. The hydrophobic polyfunctional (meth) acrylate compound may be, for example, a monomer or an oligomer obtained by polymerizing one or more monomers. The hydrophobic polyfunctional (meth) acrylate compound may be a modified product of a (meth) acrylate monomer or a (meth) acrylate oligomer, but is preferably a (meth) acrylate monomer.

In addition, when a hydrophobic polyfunctional (meth) acrylate type compound is an oligomer, it is preferable that the weight average molecular weight is 400-5000, and it is more preferable that it is 500-2000. The weight average molecular weight is a value (polystyrene conversion value) measured by gel permeation chromatography. The weight average molecular weight can be determined, for example, by using high performance liquid chromatography (“Waters 2695 (main body)” and “Waters 2414 (detector)” manufactured by Water, Japan) on a column (Shodex® GPC KF-806L (exclusion limit)). Molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm)) in series It can be specified by placing and measuring.

In the present specification, the compound being “hydrophobic” means that the ClogP value of the compound is 3.0 or more. The ClogP value of the hydrophobic polyfunctional (meth) acrylate monomer is more preferably 3.0 to 7.0, and further preferably 3.0 to 5.5. The “CLogP value” is a LogP value calculated by calculation. The CLogP value is calculated by a fragment method, an atomic approach method, or the like. To calculate the ClogP value, reference is made to the literature (C. Hansch and A. Leo, “Substitute Constants for Correlation Analysis in Chemistry and Biology” (John Wiley & Sons, the following method described in 19). A software package may be used.
Software package: Chem Draw Ultra ver. 8.0. (April 2003, CambridgeSoft Corporation, USA)
The ClogP value described in the present specification is a ClogP value calculated using the software package.

  Here, the number of (meth) acryloyl groups contained in the hydrophobic polyfunctional (meth) acrylate compound may be 2 or more, preferably 2 to 6, and more preferably 2 to 4. When the number of (meth) acryloyl groups is 2 or more, the rub resistance of the cured product and the adhesion to the recording medium tend to be good. On the other hand, when the number of (meth) acryloyl groups is 6 or less, the cured product is not excessively crosslinked, and a highly flexible cured product is easily obtained.

  Examples of hydrophobic polyfunctional (meth) acrylate compounds ((meth) acrylate monomers) include 1,10-decanediol dimethacrylate (NK ester DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 5.75). Tricyclodecane dimethanol diacrylate (SR833, manufactured by Sartomer, ClogP value: 4.69) Tricyclodecane dimethanol dimethacrylate (NK ester DCP, manufactured by Shin-Nakamura Chemical Co., ClogP value: 5.12), nonylphenol 8 Ethyloxy-modified acrylate (Miramer M166, manufactured by Miwon, ClogP value: 6.42), trimethylolpropane 3-propyloxy-modified triacrylate (Miramer M360, manufactured by Miwon, ClogP value: 4.90), 1,6-hexanediol Diak Rate (A-HD-N, Shin Nakamura Chemical Co., ClogP value: 3.08), Tricyclodecane dimethanol diacrylate (A-DCP, Shin Nakamura Chemical Co., ClogP value: 4.22), 3- Methyl-1,5-pentanediol diacrylate (SR341, manufactured by Sartomer, ClogP value: 3.01), 1,10-decanediol diacrylate (NK ester A-DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value) : 5.04), 1,9-nonanediol diacrylate (NK ester A-NOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 4.55), dioxane glycol diacrylate (A-DOG, Shin-Nakamura Chemical Co., Ltd.) Made, ClogP value: 3.12), hydroxypivalic acid neopentyl glycol diacrylate (M210, made by Miwon, Clog P value: 3.87), ditrimethylolpropane tetraacrylate (SR355, manufactured by Sartomer, ClogP value: 4.34), ethoxylated-o-phenylphenol acrylate (A-LEN-10, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP) Value: 4.22), isobornyl acrylate (A-IB, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 4.21), isostearyl acrylate (S-1800A, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 9.00) ) Etc. are included. The ink may contain only one kind of hydrophobic polyfunctional (meth) acrylate, or may contain two or more kinds.

  The content of the hydrophobic polyfunctional (meth) acrylate compound is preferably 40 to 90% by mass, more preferably 60 to 90% by mass, and 65 to 90% by mass with respect to the total mass of the ink. More preferably it is. When the ink contains two or more kinds of hydrophobic polyfunctional (meth) acrylate compounds, the total amount thereof is preferably in the above range. When the content of the hydrophobic polyfunctional (meth) acrylate compound is 40% by mass or more, the adhesion of the cured product to the recording medium tends to be good, and the rub resistance of the cured product tends to be good. On the other hand, when the content of the hydrophobic polyfunctional (meth) acrylate is 90% by mass or less, the amount of the polyfunctional vinyl ether compound is relatively increased, and the adhesion and the abrasion resistance of the cured product are easily increased. .

  As described above, a part of the polyfunctional (meth) acrylate compound may be a hydrophilic (meth) acrylate compound, that is, a polyfunctional (meth) acrylate compound having a ClogP value of less than 3. Examples of polyfunctional (meth) acrylate compounds with a ClogP value of less than 3 include ethoxylated (6) modified trimethylolpropane triacrylate (SR499, manufactured by Sartomer, ClogP value: 1.22), 2-propyloxy modified Neopentyl glycol diacrylate (SR9003, manufactured by Sartomer, ClogP value: 2.74), dipropylene glycol diacrylate (APG-100, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 1.67), tripropylene glycol diacrylate ( APG-200, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 1.82) and the like are included.

2. Polyfunctional vinyl ether compound In the present specification, the polyfunctional vinyl ether compound is a compound having at least one vinyl ether group and having at least two unsaturated double bonds, and any compound having such a structure is particularly limited. Not. The polyfunctional vinyl ether compound may be, for example, a monomer or an oligomer obtained by polymerizing one or more monomers. Moreover, although the modified product of a polyfunctional vinyl ether monomer or a polyfunctional vinyl ether oligomer may be sufficient, it is preferable that it is a polyfunctional vinyl ether monomer. Furthermore, the unsaturated double bond contained in the polyfunctional vinyl ether compound may be an unsaturated double bond derived from a (meth) acryloyl group, but any of the unsaturated double bonds contained in the polyfunctional vinyl ether compound However, it is preferable from a viewpoint of the softness | flexibility of hardened | cured material that it is a double bond derived from a vinyl ether group.

  Examples of polyfunctional vinyl ether compounds (polyfunctional vinyl ether monomers) include 2- (2-vinyloxyethoxy) ethyl (meth) acrylate, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol di Vinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, bis [4- (vinyloxy) butyl] adipate, bis [4- (vinyloxy) butyl] Succinate, bis [4- (vinyloxy) butyl] isophthalate, bis [4- (vinyloxymethyl) cyclohexylmethyl Glutarate, tris [4- (vinyloxy) butyl] trimellitate, bis [4- (vinyloxy) butyl] hexanediylbiscarbamate, bis [4- (vinyloxy) methyl] cyclohexylmethyl terephthalate, bis [4- (vinyloxy) methyl] cyclohexyl Methyl isophthalate, bis [4- (vinyloxy) butyl] (4-methyl-1,3-phenylene) -biscarbamate, and bis [4- (vinyloxy) butyl] (methylenedi-4,1-phenylene) -bis Carbamate and the like are included. The ink may contain only one kind of polyfunctional vinyl ether compound, or may contain two or more kinds.

  Among the above, the polyfunctional vinyl ether compound is preferably an ethylene oxide modified product. That is, it preferably has an ethylene oxide structure, and specifically, ethylene glycol divinyl ether, diethylene glycol divinyl ether, or triethylene glycol divinyl ether is preferable. If the polyfunctional vinyl ether compound has an ethylene oxide structure, a chain transfer reaction is likely to occur during ink curing.

  The content of the polyfunctional vinyl ether compound is preferably 1 to 30% by mass and more preferably 5 to 30% by mass with respect to the total mass of the ink. When the ink contains two or more polyfunctional vinyl ether compounds, the total amount of these is preferably in the above range. When the content of the polyfunctional vinyl ether compound is 1% by mass or more, the flexibility of the cured product tends to be good. On the other hand, when the content of the polyfunctional vinyl ether compound is 30% by mass or less, the amount of the hydrophobic polyfunctional (meth) acrylate compound is relatively increased, and the rub resistance of the cured product and the recording medium are reduced. Adhesion tends to be good.

3. Fluorescent whitening agent A fluorescent whitening agent is a compound that generally absorbs light having a wavelength of about 300 to 450 nm and emits fluorescence having a wavelength of about 400 to 500 nm. The physical principle and chemical properties of the optical brightener are described in Ullmann's Encyclopedia of Industrial Chemistry, Six Edition, Electronic Release, Wiley-VCH 1998, and the like.

  The optical brightener is not particularly limited as long as it is a compound having the above characteristics. Examples thereof include benzoxazole compounds, coumarin compounds, styrene biphenyl compounds, pyrazolone compounds, stilbene compounds, benzene and biphenyl. Styryl derivatives, bis (benzazol-2-yl) derivatives, carbostyryl, naphthalimide, derivatives of dibenzothiophene-5,5′-dioxide, pyrene derivatives, pyridotriazole and the like. The ink may contain only one type of fluorescent brightening agent, or may contain two or more types. Of these, benzoxazole compounds are preferred from the viewpoint of suppressing ink coloring.

  The benzoxazole-based fluorescent brightener includes a benzoxazole-based compound represented by the following general formula (1).

上記一般式（１）において、Ｒ_１〜Ｒ_８はそれぞれ独立に、水素原子またはアルキル基を表す。ただし、Ｒ_１〜Ｒ_８から選ばれる２以上の基が結合して環を形成していてもよい。

In the general formula (1), R _{1 to} R ₈ each independently represents a hydrogen atom or an alkyl group. However, two or more groups selected from R _{1 to} R ₈ may be bonded to form a ring.

  The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and may have any of a linear, branched, or cyclic structure. In addition, the alkyl group may be substituted. Examples of the substituent include a carboxyl group, an alkoxy group, a hydroxyl group, a halogen atom and the like.

式（２）〜（５）における＊は、一般式（１）におけるベンゾオキサゾール基との結合手を表す。 On the other hand, in the general formula (1), A represents any linking group represented by the following formulas (2) to (5).

* In the formulas (2) to (5) represents a bond with the benzoxazole group in the general formula (1).

  Among these, a fluorescent brightening agent having a structure represented by the formula (4) is particularly preferable from the viewpoint of improving the adhesion of the cured product.

  Examples of commercially available products of the benzoxazole-based optical brightener represented by the general formula (1) include FLUORESCENT BRIGHTTENER KCB (manufactured by Xcolor Pigment), wherein A is a structure of the formula (2), FLUORESCENT BRIGHTTENER PF (manufactured by Xcolor Pigment) in which A is the structure of formula (3), FLUORESCENT BRIGHTTENER OB and FLUORESCENT BRIGHTTENER PB (both are Xcolor, P FLUORESCENT BRIGHTTENER OB-1 and FLUORESCENT BRIGHTTENER KSN (both made by Xcolor Pigment) are included, where A in the formula is the structure of formula (5) .

  The content of the optical brightener is preferably 0.01% by mass or more and 1.0% by mass with respect to the total mass of the ink, and more preferably 0.05% by mass or more and 0.5% by mass or less. Preferably, it is 0.05 mass% or more and 0.2 mass% or less. When the ink contains two or more fluorescent brighteners, the total amount of these is preferably within the above range. When the content of the optical brightener is 0.01% by mass or more, the optical brightener functions sufficiently as a chain transfer agent, and the crosslink density of the cured product tends to increase. On the other hand, if the crosslink density of the cured product is excessively increased, the flexibility of the cured product is reduced. The balance with property and adhesion is improved. Further, when the amount of the fluorescent brightening agent is within the above range, in the case of color ink, the influence on the color tone of the cured film can be reduced.

4). Radical polymerization initiator The ink of the present invention may contain a radical polymerization initiator. When the ink is cured with an electron beam or the like, it is not always necessary to include a radical polymerization initiator. However, when the ink is cured with ultraviolet light or the like, it is preferable to include a radical polymerization initiator. The ink may contain only one kind of radical polymerization initiator, or may contain two or more kinds.

  As the radical polymerization initiator, there are a Type I type initiator called an intramolecular bond cleavage type and a Type II type initiator called a hydrogen abstraction type. Examples of the intramolecular bond cleavage type (Type I type) radical polymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1- (4-isopropyl Phenyl) -2-hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2 An acetophenone-based polymerization initiator containing morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, etc .; benzoin, benzoin methyl ether, Polymerization initiators for benzoins, including benzoin isopropyl ether; , Polymerization initiator acylphosphine oxide containing 4,6-trimethyl benzoin diphenylphosphine oxide, and the like; include and the like; benzyl and methyl phenylglyoxylate ester.

  Examples of a hydrogen abstraction type (Type II type) radical polymerization initiator include benzophenone, methyl 4-phenylbenzophenone, o-benzoylbenzoate, 4,4′-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4′-methyl. Benzophenone-based polymerization initiators including diphenyl sulfide, acrylated benzophenone, 3,3 ′, 4,4′-tetra (t-butylperoxycarbonyl) benzophenone, 3,3′-dimethyl-4-methoxybenzophenone; thioxanthone 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2-dodecylthioxanthone, , 3-diethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1-chloro-4-propoxythioxanthone, 2-cyclohexylthioxanthone, 4-cyclohexylthioxanthone, 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone 3- (2-methoxyethoxycarbonyl) thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxy Carbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfylthioxyl , 3,4-di [2- (2-methoxyethoxy) ethoxycarbonyl] thioxanthone, 1-ethoxycarbonyl-3- (1-methyl-1-morpholinoethyl) thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6- (1,1-dimethoxybenzyl) thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboximide, n-octylthioxanthone- 3,4-dicarboximide, N- (1,1,3,3-tetramethylbutyl) thioxanthone-3,4-dicarboximide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6- Ethoxycarbonyl-2-methyl Ruthioxanthone, thioxanthone-2-polyethylene glycol ester, 2-hydroxy-3- (3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy) -N, N, N-trimethyl-1-propanaminium Thioxanthone polymerization initiators including chloride, etc .; Michler ketone, aminobenzophenone polymerization initiators including 4,4′-diethylaminobenzophenone, etc .; 10-butyl-2-chloroacridone; 2-ethylanthraquinone; 10-phenanthrenequinone; camphorquinone; and the like.

上記式（６）において、Ｒ^１およびＲ^２はそれぞれ独立に、炭素数１〜５のアルキル基、またはハロゲン原子を表し、ｃは２〜４の整数を表し、ａは０〜４の整数を表し、ｂは０〜３の整数を表す。ａおよび／またはｂが２以上の整数のとき、複数のＲ^１および／またはＲ^２は、同一であってもよく、異なっていてもよい。さらに、Ｒ^３は炭化水素鎖、エーテル結合、エステル結合のいずれかを少なくとも含み、炭素数２〜３００のｃ価の連結基を表す。） As the thioxanthone-based polymerization initiator, a compound represented by the following formula (6) can also be preferably used.

In the formula (6), R ¹ and R ² each independently represents an alkyl group having 1 to 5 carbon atoms or a halogen atom, c represents an integer of 2 to 4, and a represents an integer of 0 to 4. And b represents an integer of 0 to 3. When a and / or b is an integer of 2 or more, a plurality of R ¹ and / or R ² may be the same or different. Further, R ³ represents at least one of a hydrocarbon chain, an ether bond, and an ester bond, and represents a c-valent linking group having 2 to 300 carbon atoms. )

  The molecular weight of the thioxanthone-based polymerization initiator represented by the above formula (6) is preferably 500 to 3000, more preferably 800 to 2500, and still more preferably 1000 to 2000.

  The thioxanthone compound represented by the above formula (6) may be a commercially available product, and examples thereof include SPEEDCURE 7010 (manufactured by Lambson), OMNIPOL TX (manufactured by IGM Resin), and the like.

  The radical polymerization initiator preferably includes a high molecular weight type thioxanthone type polymerization initiator represented by the above formula (6). If the ink contains a high molecular weight type polymerization initiator, the ink is difficult to migrate, and the ink Odor and the like can be suppressed.

  The content of the radical polymerization initiator depends on the actinic ray to be irradiated and the type of the actinic ray polymerizable compound, but the total amount is preferably 1 to 10% by mass, and preferably 3 to 10% by mass. Is more preferable. On the other hand, the content of the intramolecular bond cleavage type (Type I type) radical polymerization initiator among the above is preferably 0.1 to 3.5% by mass with respect to the total mass of the ink, from the viewpoint of adhesion, More preferably, it is 1-3.5 mass%. When the ink contains two or more Type I type radical polymerization initiators, the total amount of these is preferably in the above range.

  The ink may contain a polymerization initiation assistant in addition to the polymerization initiator. A tertiary amine compound is mentioned as an example of the polymerization initiation assistant, and among these, an aromatic tertiary amine compound is particularly preferable. Examples of aromatic tertiary amine compounds include N, N-dimethylaniline, N, N-diethylaniline, N, N-dimethyl-p-toluidine, N, N-dimethylamino-p-benzoic acid ethyl ester, N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester, N, N-dihydroxyethylaniline, triethylamine, N, N-dimethylhexylamine and the like are included. Among these, N, N-dimethylamino-p-benzoic acid ethyl ester and N, N-dimethylamino-p-benzoic acid isoamyl ethyl ester are preferable. One kind of these polymerization initiation assistants may be contained in the ink, or two or more kinds thereof may be contained.

  The content of the polymerization initiation assistant is preferably 0.1% by mass to 5% by mass with respect to the total mass of the ink, although it depends on the active light to be irradiated and the type of the active light polymerizable compound.

5. Amine-modified (meth) acrylate oligomer The ink may contain an amine-modified (meth) acrylate oligomer. When the ink contains an amine-modified (meth) acrylate oligomer, it becomes easy to trap oxygen or the like on the surface of the ink droplet by the amino group. As a result, oxygen inhibition is less likely to occur during ink curing, and ink curability is improved. Furthermore, when the cured product of the ink contains an amine-modified (meth) acrylate oligomer, the low molecular weight component in the cured product is difficult to migrate, and further the odor of the cured product is easily reduced.

  The amine-modified (meth) acrylate oligomer is not particularly limited as long as it is an oligomer having at least one amino group and at least one (meth) acryloyl group.

  On the other hand, the number of (meth) acryloyl groups contained in the amine-modified (meth) acrylate oligomer is not particularly limited as long as it is 1 or more, but is preferably 1 to 6, and more preferably 2 to 4. When the number of (meth) acryloyl groups is within the above range, the amine-modified (meth) acrylate oligomer easily reacts with the above-mentioned hydrophobic polyfunctional (meth) acrylate compound or polyfunctional vinyl ether compound. Furthermore, the viscosity of the ink tends to be in an appropriate range. Furthermore, it is easy to obtain a migration suppression effect.

  The amine-modified (meth) acrylate oligomer may be synthesized by polymerizing a desired monomer, or may be a commercially available one. Examples of commercially available amine-modified (meth) acrylate oligomers include GENOMER 5161 and GENOMER 5275 (both manufactured by RAHN); CN371, CN373, CN383, CN384, CN386, CN501, CN550, CN551 (all manufactured by Sartomer); EBECRYL7100 , EBECRYL80, EBECRYL81, EBECRYL83, EBECRYL84, EBECRYLP115 (all manufactured by Daicel Cytec); Photomer5096, Photomer5662, Photomer5930 (all manufactured by Cognis); DoublecureEPD, DoublecureOPD, Doublecure115, Doublecure225, Doublecure645, PolyQ222, PolyQ226, PolyQ224, PolyQ101 (all manufactured DoubleBondChemicals Corporation). The ink may contain only one kind of amine-modified (meth) acrylate oligomer, or may contain two or more kinds.

  The content of the amine-modified (meth) acrylate oligomer is preferably 3 to 30% by mass and more preferably 5 to 20% by mass with respect to the total mass of the ink. When the ink contains two or more amine-modified (meth) acrylate oligomers, the total amount of these is preferably in the above range. When the content of the amine-modified (meth) acrylate oligomer is in this range, the curability of the cured product of the ink is likely to be good, and migration and odor are also easily suppressed.

6). Gelling agent The ink of the present invention may contain a gelling agent. When the ink contains a gelling agent, the ink can undergo a sol-gel phase transition as the temperature changes.

  The gelling agent is preferably a compound that can be crystallized in ink, and further preferably one that forms a space three-dimensionally surrounded by crystals of the gelling agent. In this way, a structure in which a space in which the crystal of the gelling agent is three-dimensionally surrounded is sometimes referred to as a “card house structure”. When the card house structure is formed, some or all of the liquid components such as hydrophobic polyfunctional (meth) acrylate compounds and polyfunctional vinyl ether compounds are embedded in the space three-dimensionally surrounded by the crystal of the gelling agent. Becomes easier to hold. As a result, the ink droplets are easily pinned, and the coalescence of the droplets is easily suppressed. In order to form the card house structure, it is preferable that the hydrophobic polyfunctional (meth) acrylate compound or polyfunctional vinyl ether compound dissolved in the ink and the gelling agent are compatible.

  Examples of such a gelling agent include dilignoseryl ketone (C24-C24 (the numerical value represents the number of carbon atoms; the same applies hereinafter)), dibehenyl ketone (C22-C22), distearyl ketone (C18-C18), Diaicosyl ketone (C20-C20), dipalmityl ketone (C16-C16), dimyristyl ketone (C14-C14), dilauryl ketone (C12-C12), lauryl myristyl ketone (C12-C14), lauryl palmityl Ketone (C12-C16), myristyl palmityl ketone (C14-C16), myristyl stearyl ketone (C14-C18), myristyl behenyl ketone (C14-C22), palmityl stearyl ketone (C16-C18), valmityl behenyl ketone ( C16-C22), stearyl behenyl ketone (C Aliphatic ketone compounds such as 8-C22); behenyl behenate (C21-C22), icosyl icosylate (C19-C20), stearyl stearate (C17-C18), palmityl stearate (C17-C16), lauryl stearate (C17-C12), cetyl palmitate (C15-C16), stearyl palmitate (C15-C18), myristyl myristate (C13-C14), cetyl myristate (C13-C16), octyldodecyl myristate (C13-C20) ), Stearyl oleate (C17-C18), stearyl erucate (C21-C18), stearyl linoleate (C17-C18), behenyl oleate (C18-C22), myricyl serinate (C25-C16), stearyl montanate (C2 -C18), aliphatic ester compounds such as behenyl montanate (C27-C22), arachidyl linoleate (C17-C20), palmitanyl triacontanoate (C29-C16); petroleum oils such as paraffin wax, microcrystalline wax, petrolactam, etc. Waxes such as candelilla wax, carnauba wax, rice wax, tree wax, jojoba oil, jojoba solid wax, and jojoba ester; animal waxes such as beeswax, lanolin and whale wax; montan wax and hydrogen Mineral waxes such as modified waxes; hardened castor oil or hardened castor oil derivatives; modified waxes such as montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives or polyethylene wax derivatives; behenic acid, arachi Higher fatty acids such as diacid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid and erucic acid; higher alcohols such as stearyl alcohol and behenyl alcohol; hydroxystearic acid such as 12-hydroxystearic acid; 12-hydroxystearic acid Acid derivatives: Fatty acid amides such as lauric acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, ricinoleic acid amide, 12-hydroxystearic acid amide (for example, Nikka Amide series manufactured by Nippon Kasei Co., Ltd., Ito Oil Co., Ltd.) ITOWAX series manufactured by Kao Corporation, FATTYAMID series, etc.); N-substituted fatty acid amides such as N-stearyl stearamide, N-oleyl palmitate amide; N, N′-ethylenebisstearylamide, N Special fatty acid amides such as N'-ethylenebis-12-hydroxystearylamide and N, N'-xylylenebisstearylamide; higher amines such as dodecylamine, tetradecylamine or octadecylamine; stearyl stearic acid, oleyl palmitic acid , Fatty acid ester compounds such as glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester (for example, EMALLEX series manufactured by Nihon Emulsion Co., Ltd. (Poem series, etc.); Esters of sucrose fatty acids such as sucrose stearic acid and sucrose palmitic acid (eg Ryoto Sugar Ester series Mitsubishi Chemical Synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax (UNILIN series etc. manufactured by Baker-Petrolite); dimer acid; dimer diol (such as PRIDA series produced by CRODA); stearic acid Fatty acid inulin such as inulin; Fatty acid dextrin such as dextrin palmitate and dextrin myristate (such as Leopard Series manufactured by Chiba Flour Mills); glyceryl behenate; eicosane polyglyceryl behenate; Nocort series manufactured by Nisshin Oillio Co., Ltd. Amide compounds such as N-lauroyl-L-glutamic acid dibutylamide and N- (2-ethylhexanoyl) -L-glutamic acid dibutylamide (available from Ajinomoto Fine Techno); 1,3: 2,4 -Dibenzylidene sorbitols such as bis-O-benzylidene-D-glucitol (Gelol D available from Nippon Kayaku); JP-A-2005-126507, JP-A-2005-255821 and JP-A-2010-111170 And the like, and the like.

  Examples of commercially available products of the aliphatic ketone include 18-Pentriacontanon (made by Alfa Aeser), Hentriacontan-16-on (made by Alfa Aeser), Kao wax T1 (made by Kao Corporation), and the like. On the other hand, examples of commercially available aliphatic ester compounds include Unistar M-2222SL (manufactured by NOF Corporation), EXCEPARL SS (manufactured by Kao Corporation), EMALEX CC-18 (manufactured by Nippon Emulsion Co., Ltd.), Amreps PC ( High Alcohol Industry Co., Ltd.), Exepearl MY-M (Kao Co., Ltd.), Spalm Aceti (Nippon Oil Co., Ltd.), EMALEX CC-10 (Nihon Emulsion Co., Ltd.) and the like are included. Since these commercial products are often a mixture of two or more types, they may be separated and purified as necessary.

  Here, the gelling agent is preferably a compound having a linear or branched carbon chain having 14 or more carbon atoms, preferably 14 to 30 carbon atoms, an aliphatic ketone, an aliphatic ester, a higher fatty acid, More preferably, it is either a higher alcohol or an amide compound. When the gelling agent contains a linear carbon chain having 14 or more carbon atoms, the above-mentioned “card house structure” is easily formed.

  The ink is also used for the purpose of adjusting crystal growth of the gelling agent, such as glycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, ethylene glycol fatty acid ester, polyoxyethylene fatty acid ester (for example, Japan). Emulle series manufactured by Emulsion, Rikenmar series manufactured by Riken Vitamin, Poem series manufactured by Riken Vitamin, etc.)

  The content of the gelling agent is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 7% by mass, and 1.5% by mass with respect to the total mass of the ink. More preferably, it is -5 mass%. When the ink contains two or more gelling agents, the total amount of these is preferably within the above range. When the amount of the gelling agent is within the above range, the ink easily undergoes sol-gel phase transition, and the pinning property of the ink is enhanced.

7). Other Components In addition to the components described above, the ink of the present invention further includes other components such as a coloring material, a dispersant, an antioxidant, a polymerization inhibitor, a surfactant, and other polymerizable components. Also good. The ink may contain only one kind of these components, or may contain two or more kinds.

  The color material may be either a dye or a pigment, but from the viewpoint of forming an image having good weather resistance, the color material is preferably a pigment. The pigment can be selected from, for example, a yellow pigment, a red or magenta pigment, a blue or cyan pigment, and a black pigment according to the color of the image to be formed.

  When the ink contains a coloring material, the content (total amount) is preferably 0.1% by mass or more and 20% by mass or less, and 0.4% by mass or more and 10% by mass or less with respect to the total mass of the ink. More preferably.

  Examples of dispersants include hydroxyl group-containing carboxylic acid esters, salts of long chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long chain polyaminoamides and polar acid esters, high molecular weight unsaturated. Acid ester, polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, poly Oxyethylene nonyl phenyl ether, stearylamine acetate and the like are included.

  Content of a dispersing agent can be 20 mass% or more and 70 mass% or less with respect to the total mass of a pigment, for example.

  Examples of the antioxidant include hindered amine antioxidants, thioether antioxidants, phenolic antioxidants, phosphoric acid antioxidants, and the like. The content of the antioxidant is preferably 0.01 to 1% by mass and more preferably 0.1 to 0.5% by mass with respect to the total mass of the ink. When the ink contains an antioxidant, oxygen inhibition is less likely to occur when the ink is cured, and the rub resistance is likely to increase. Moreover, it is preferable to contain a phenolic antioxidant especially among the above.

  A phenolic antioxidant has a structure in which one of hydrogen atoms forming an aromatic ring is substituted with a hydroxyl group (hereinafter also simply referred to as “phenolic structure”), and can exhibit an antioxidant function. If it is.

  The phenolic antioxidant may be a hindered phenolic antioxidant having a t-butyl group in the ortho position (one or both) as viewed from the hydroxyl group of the phenol structure, or may be an antioxidant other than the hindered phenolic. Good. In addition, the phenolic antioxidant may have an ether group, a thioether group, an ester group, an amide group, or the like in the molecule.

  The phenolic antioxidant may be a monofunctional compound having only one phenol structure in the molecule, but is preferably a polyfunctional compound having two or more phenol structures in the molecule. The polyfunctional phenolic antioxidant becomes a cross-linking agent by radical transfer when oxygen in the ink is trapped. Therefore, the crosslinking degree of a polyfunctional (meth) acrylate compound or a polyfunctional vinyl ether compound can be increased by such an antioxidant.

  When the phenolic antioxidant is a polyfunctional compound, the linking group that links two or more phenol structures may be located in the ortho position as viewed from the hydroxyl group of the phenol structure, or in the para position. May be. The linking group can be an alkylene group, an ether group, a thioether group, or a divalent group in which these are linked. The linking group may have a structure in which an amide group, an aromatic ring, or the like is connected to an alkylene group. Examples of the alkylene group include an alkyl group having 1 to 20 carbon atoms.

  Examples of the hindered phenolic antioxidant, which is a kind of the above-mentioned phenolic antioxidant, include bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ Ethylenebis (oxyethylene)], 1,6-hexanediol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2′-thiodiethylbis [3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], octyl-3,5-di-tert-butyl-4-hydroxy-hydrosilicic acid, 3- (3,5-di-tert-butyl- 4-hydroxyphenyl) stearyl propionate, pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate], 2-tert-butyl-4-methyl-6- (2-hydroxy-3-tert-butyl-5-methylbenzyl) phenyl acrylate, 1′-hydroxy acrylate [2,2′-ethylidenebis [ 4,6-bis (1,1-dimethylpropyl) benzene]]-1-yl, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 4,4′-butylidenebis (6-tert -Butyl-m-cresol), 4,4'-thiobis (6-tert-butyl-m-cresol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane , N, N′-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], 2,4,6-tris (3 ′, '-Di-tert-butyl-4'-hydroxybenzyl) mesitylene, 1,3,5-tris [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] -1,3 , 5-Triazine-2,4,6 (1H, 3H, 5H) -trione, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane and the like.

  On the other hand, examples of phenolic antioxidants other than hindered phenols include 2,4-bis (octylthiomethyl) -6-methylphenol.

  Examples of commercially available phenolic antioxidants include IRGANOX 1520L (manufactured by BASF), NOCRACK NS-6 (manufactured by Ouchi Shinsei Chemical), Sumilizer GS, Sumilizer GM, Sumilizer GS (F), Sumilizer MDP- S (both manufactured by Sumitomo Chemical Co., Ltd.), Seenox 224M (manufactured by Sipro Kasei), IRGANOX 1076, IRGANOX 1330, IRGANOX L109, IRGANOX 1098, IRGANOX 1135 (both manufactured by BASF), and ADK STAB AO-20, ADK STAB AO-20 30, ADK STAB AO-40, ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-70, ADK STAB AO-80, ADK STAB AO-330 (both manufactured by ADEKA) ), Sumilizer BBM-S, Sumilizer WX-R, Summarizer WX-RA, Sumilizer WX-RC, Sumilizer GA-80 (both manufactured by Sumitomo Chemical Co., Ltd.), Nocrack NS-30, Nocrack 300 (both manufactured by Ouchi Shinsei Chemical Co., Ltd.) Etc. are included.

（式中、
Ｒ^９およびＲ^１０はそれぞれ独立に、炭素数１以上４以下のアルキル基であり、
ｎは２〜４の整数であり、
Ｌは、ｎ価の連結基である。） A particularly preferred antioxidant is a phenolic antioxidant represented by the following general formula (7).

(Where
R ⁹ and R ¹⁰ are each independently an alkyl group having 1 to 4 carbon atoms,
n is an integer of 2 to 4,
L is an n-valent linking group. )

  L can be an alkylene group having 1 to 10 carbon atoms, or a group in which a plurality of alkylene groups (preferably having 1 to 10 carbon atoms) are linked by a thioether group or an ether group.

  Examples of commercially available antioxidants represented by the general formula (7) include IRGANOX 245, IRGANOX 259, IRGANOX L109, IRGANOX 1035, and IRGANOX 1010 (both manufactured by BASF), ADK STAB AO-70, and the like. .

  Examples of polymerization inhibitors include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone , Nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cupron, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino- 1,3-dimethylbutylidene) aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraloxime, methyl ethyl ketoxime, and cyclohexanone oxy Beam and the like are included.

  Examples of surfactants include anionic surfactants including dialkyl sulfosuccinates, alkyl naphthalene sulfonates, fatty acid salts and the like; polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, And nonionic surfactants including polyoxyethylene / polyoxypropylene block copolymers and the like; cationic surfactants including alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants; Is included.

  Examples of commercially available silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, manufactured by Shin-Etsu Chemical, BYK307, BYK345, BYK347 and BYK348, manufactured by Big Chemie ("BYK "Is a registered trademark of the same company), as well as TSF4452, manufactured by Toshiba Silicone.

  The content of the surfactant is preferably 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.

  Moreover, in the range which does not impair the effect and objective of this invention, polymeric components other than the above-mentioned polyfunctional (meth) acrylate type compound and a polyfunctional vinyl ether type compound may be included. Specifically, a monofunctional (meth) acrylate compound, a monofunctional vinyl ether compound, or the like may be included. For example, examples of monofunctional (meth) acrylate compounds include phenoxyethyl acrylate (SR399NS Sartomer). Furthermore, examples of the monofunctional vinyl ether compound include diethylene glycol monovinyl ether (DEGV).

8). Physical properties of actinic ray curable ink jet ink The ink of the present invention preferably has a viscosity at the temperature of the ink jet head of 3 mPa · s or more and 20 mPa · s or less from the viewpoint of further improving the dischargeability from the ink jet head. . For example, the temperature of the inkjet head can be about 50 ° C. when the ink does not contain a gelling agent, and about 80 ° C. when the ink contains a gelling agent.

  From the viewpoint of further improving the dischargeability from the inkjet head, the average particle diameter of the pigment particles when the ink contains a pigment is preferably 0.08 μm or more and 0.5 μm or less, and the maximum particle diameter is 0.3 μm or more. It is preferable that it is 10 micrometers or less. The average particle diameter of the pigment particles in the present specification means a value obtained by a dynamic light scattering method using Data Sizer Nano ZSP, manufactured by Malvern. Note that the ink containing the color material has a high concentration and does not transmit light with this measuring instrument. Therefore, the ink is diluted 200 times before measurement. The measurement temperature is room temperature (25 ° C.).

9. Preparation method of actinic ray curable ink-jet ink The ink of the present invention comprises the above-mentioned hydrophobic polyfunctional (meth) acrylate compound, polyfunctional vinyl ether compound, and fluorescent brightener, and a polymerization initiator or gel as necessary. It can be prepared by mixing the agent and any other components while heating. At this time, it is preferable to filter the obtained mixed solution with a predetermined filter. When preparing an ink containing a pigment and a dispersant, a pigment dispersion in which the pigment and the dispersant are dispersed in an actinic ray polymerizable compound is prepared in advance, and the remaining components are added thereto. You may mix, heating.

  The pigment and the dispersant can be dispersed by, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker.

10. Use of actinic ray curable ink-jet ink As described above, the ink of the present invention has high flexibility, high adhesion to a recording medium, and can form an image having high abrasion resistance. Therefore, it can be applied to printing of various packages and various printing.

  As a method for using ink, ink droplets are ejected from the nozzles of an inkjet head, landed on a recording medium, and then irradiated with actinic rays to cure the ink droplets.

  The inkjet head may be either an on-demand system or a continuous system. Examples of on-demand inkjet heads include single-cavity, double-cavity, vendor-type, piston-type, electro-mechanical conversion methods including shear mode and shared wall types, and thermal inkjet types and bubble jets ( An electric-heat conversion system including a registered trademark type is included. Further, the inkjet head may be either a scanning type or a line type.

  Here, the ejection stability of the ink can be enhanced by ejecting heated ink from the inkjet head. The temperature of the ink when ejected from the inkjet head is preferably 35 ° C. or more and 100 ° C. or less, and more preferably 35 ° C. or more and 80 ° C. or less in order to further improve ejection stability.

  Note that the temperature of the recording medium on which the ink droplets are landed is not particularly limited. However, in terms of accelerating the crystallization of the fluorescent brightening agent or causing the ink to undergo a sol-gel phase transition when the ink contains a gelling agent. To the melting point of the gelling agent or lower, preferably 40 ° C. or lower, more preferably 35 ° C. or lower.

  The amount of droplets at the time of ink ejection is preferably 2 pL or more and 50 pL or less, and more preferably 2 to 20 pL, from the viewpoint of recording speed and image quality.

  Further, the recording medium on which the ink is landed is not particularly limited. Examples of recording media include art paper, coated paper, lightweight coated paper, finely coated paper cast paper, and absorbent media including coated and uncoated paper including cardboard, polyester, polyvinyl chloride, polyethylene , Polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, non-absorbent recording medium (plastic substrate) composed of plastics including polyethylene terephthalate and polybutadiene terephthalate, and metals and glass Non-absorbing inorganic recording media such as

  On the other hand, the actinic ray irradiated to the ink droplet is appropriately selected depending on the type of the actinic ray polymerizable compound, and can be an ultraviolet ray or an electron beam.

When the actinic ray is ultraviolet light, examples of the light source include fluorescent tubes (low pressure mercury lamps, germicidal lamps), cold cathode tubes, ultraviolet lasers, low pressure, medium pressure, high pressure mercury lamps having an operating pressure of several hundred Pa to 1 MPa. , Metal halide lamps and LEDs. From the viewpoint of curing the ink efficiently, a light source capable of irradiating ultraviolet rays with an illuminance of 100 mW / cm ² or more; specifically, a high-pressure mercury lamp, a metal halide lamp, an LED or the like is preferable, and a viewpoint that power consumption is low. Therefore, the LED is more preferable. Specifically, a 395 nm, water-cooled LED manufactured by Phoseon Technology can be used.

Also, if active ray is ultraviolet light quantity at the time of irradiation is preferably 200 mJ / cm ² or more 1000 mJ / cm ^2. When the light amount is 200 mJ / cm ² or more, the actinic ray-polymerizable compound can be sufficiently polymerized and the hardness of the cured product can be sufficiently increased. On the other hand, if the amount of light is excessive, the recording medium may be affected. However, if the amount of light is 1000 mJ / cm ² or less, such a problem is unlikely to occur. From this point of view, the amount of active light to be irradiated is more preferably at most 300 mJ / cm ² or more 800 mJ / cm ^2, and more preferably 350 mJ / cm ² or more 500 mJ / cm ² or less.

  On the other hand, when the actinic ray is an electron beam, examples of the electron beam irradiation device include electron beam irradiation devices such as a scanning method, a curtain beam method, and a broad beam method. It is preferable that the electron beam irradiation apparatus is of the type. Examples of the electron beam irradiation apparatus include “Curetron EBC-200-20-30” manufactured by Nissin High Voltage Co., Ltd., “Min-EB” manufactured by AIT Co., Ltd., and the like.

  When the actinic ray is an electron beam, the acceleration voltage for electron beam irradiation is preferably 30 to 250 kV and more preferably 30 to 100 kV in order to perform sufficient curing. When the acceleration voltage is 100 to 250 kV, the electron beam irradiation amount is preferably 30 to 100 kGy, and more preferably 30 to 60 kGy.

  From the viewpoint of suppressing oxygen inhibition during irradiation with actinic rays, the oxygen partial pressure of the atmosphere in which actinic rays are irradiated is preferably 0.15 atm or less. The method of lowering the partial pressure of oxygen to 0.15 atm or less may be a method of reducing the atmospheric pressure, or a method of filling an inert gas such as nitrogen or argon in the atmosphere. The oxygen partial pressure during irradiation with actinic rays is more preferably 0.10 atm or less, further preferably 0.08 atm or less, and particularly preferably 0.05 atm or less.

  In addition, when an inert gas is filled in an atmosphere irradiated with actinic rays, the oxygen concentration in the atmosphere is preferably controlled to 0.01 to 15% by volume, more preferably 0.03 to 10% by volume. Preferably, it is more preferably controlled to 0.05 to 8% by volume, and particularly preferably 0.1 to 5% by volume.

  Here, the timing of irradiating the ink that has landed on the recording medium with actinic rays is not particularly limited, but normally, the actinic rays are irradiated within 0.001 seconds to 2.0 seconds after the ink lands on the recording medium. In view of forming a high-definition image, it is more preferable to irradiate between 0.001 seconds and 1.0 seconds.

  In addition, it is preferable that the total ink film thickness after hardening is 2-25 micrometers. The “total ink film thickness” is the maximum value of the ink film thickness drawn on the recording medium.

  In the following, specific examples of the present invention will be described. These examples do not limit the scope of the present invention.

1. 1. Preparation of actinic ray curable inkjet ink 1-1. Materials The following materials were used for the preparation of the actinic ray curable inkjet ink.

[Hydrophobic polyfunctional (meth) acrylate compounds]
A-HD-N (1,6-hexanediol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 3.08)
SR833 (tricyclodecane dimethanol diacrylate, manufactured by Sartomer, Clog P value: 4.69)
DOD-N (1,10-decanediol dimethacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., ClogP value: 5.75)
SR341 (3-methyl-1,5-pentanediol diacrylate, manufactured by Sartomer, ClogP value: 3.01)
M210 (Neopentyl glycol diacrylate hydroxypivalate (M210, manufactured by Miwon, Clog P value: 3.87)
A-DOG (dioxane glycol diacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., Clog P value: 3.12)

[Other (meth) acrylate compounds]
SR499 (ethoxylated (6) modified trimethylolpropane triacrylate, manufactured by Sartomer, ClogP value: 1.22)
SR339NS (phenoxyethyl acrylate, manufactured by Sartomer, ClogP value: 2.46)

[Vinyl ether compounds]
・ TEGDVE (triethylene glycol divinyl ether, manufactured by Nippon Carbide Industries Co., Ltd.)
VEEA (acrylic acid 2- (2-vinyloxyethoxy) ethyl, manufactured by Nippon Shokubai Co., Ltd.)
・ DEGV (diethylene glycol monovinyl ether, manufactured by Maruzen Petrochemical Co., Ltd.)

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＦＰ−１２７（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるスチルベン系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＯＢＫ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるスチルベン系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＯＢ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるベンゾオキサゾール系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＯＢ−１（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるベンゾオキサゾール系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＰＦ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるベンゾオキサゾール系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＰＢ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるベンゾオキサゾール系化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＫＣＢ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、ベンゾオキサゾール系化合物、下記式で表される化合物）

・ＦＬＵＯＲＥＳＣＥＮＴ ＢＲＩＧＨＴＥＮＥＲ ＫＳＮ（ＸｃｏｌｏｒＰｉｇｍｅｎｔ社製、下記式で表されるベンゾオキサゾール系化合物）

[Fluorescent brightener]
・ Hakkol P (manufactured by Showa Chemical Industry Co., Ltd., Coumarin compound, compound represented by the following formula)

FLUORESCENT BRIGHTTENER FP-127 (manufactured by Xcolor Pigment, a stilbene compound represented by the following formula)

・ FLUORESCENT BRIGHTTENER OBK (manufactured by Xcolor Pigment, stilbene compound represented by the following formula)

-FLUORESCENT BRIGHTTENER OB (manufactured by Xcolor Pigment, a benzoxazole-based compound represented by the following formula)

・ FLUORESCENT BRIGHTTENER OB-1 (manufactured by Xcolor Pigment, a benzoxazole-based compound represented by the following formula)

-FLUORESCENT BRIGHTTENER PF (manufactured by Xcolor Pigment, a benzoxazole-based compound represented by the following formula)

・ FLUORESCENT BRIGHTTENER PB (manufactured by Xcolor Pigment, a benzoxazole-based compound represented by the following formula)

-FLUORESCENT BRIGHTTENER KCB (manufactured by Xcolor Pigment, benzoxazole compound, compound represented by the following formula)

-FLUORESCENT BRIGHTTENER KSN (manufactured by Xcolor Pigment, a benzoxazole-based compound represented by the following formula)

[Amine-modified (meth) acrylate oligomer]
・ CN371 (manufactured by Sartomer)
・ EBECRYL 7100 (manufactured by Daicel Ornex)
・ EBECRYL 80 (manufactured by Daicel Ornex)

[Radical polymerization initiator]
DAROCURE TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF, Type I type)
IRGACURE 819 (bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, manufactured by BASF, Type I type)
-SpeedCure 7010 (manufactured by Lambson, Type II)
SpeedCure ITX (2-Isoprothioxanthone, manufactured by Lambson, Type II)
[Gelling agent]
・ Kao wax T1 (distearyl ketone, manufactured by Kao Corporation)
・ Exepal SS (stearyl stearate, manufactured by Kao Corporation)
[Others]
(Antioxidant)
Irganox 1010 (BASF)
(Polymerization inhibitor)
・ Irgastab UV-10 (manufactured by BASF)
(Pigment dispersant)
・ EFKA4130 (BASF)
(Pigment)
・ Pigment Blue 15: 4 (manufactured by Dainichi Seika Co., Ltd.)

1-2. Preparation of Cyan Pigment Dispersion A cyan pigment dispersion was prepared according to the following procedure. 9 parts by mass of EFKA4130 (manufactured by BASF) which is a pigment dispersant and 71 parts by mass of A-HD-N (manufactured by Shin-Nakamura Chemical Co., Ltd.) which is an actinic ray polymerizable compound are placed in a stainless steel beaker and heated at 65 ° C. The mixture was heated and stirred for 1 hour while heating on the plate. The mixed liquid was cooled to room temperature, and further, 20 parts by mass of Pigment Blue 15: 4 (manufactured by Dainichi Seika Co., Ltd.) as a pigment was added. The solution was put in a glass bottle together with 200 g of zirconia beads having a diameter of 0.5 mm, sealed, and dispersed in a paint shaker for 5 hours. Thereafter, the zirconia beads were removed to obtain a cyan pigment dispersion.

1-3. Preparation of actinic ray curable inkjet ink According to the composition described in Tables 1 to 3 below, each component and the pigment dispersion were mixed, heated to 80 ° C. and stirred. Thereafter, the mixture was heated and filtered through a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVANTEC to obtain inks of Examples 1 to 28 and Comparative Examples 1 to 4. In addition, the component amount of a table | surface is the mass%.

2. Image formation [Image formation method]
A solid image of 5 cm × 5 cm was formed on an OK top coat (US basis weight 128 g / m ² , manufactured by Oji Paper Co., Ltd.) using each of the actinic radiation curable inkjet inks described in Tables 1 to 3. . As the discharge recording head of the line type ink jet recording apparatus, a KM 512LH (nozzle number: 512 nozzles, nozzle pitch: 360 npi) piezo head manufactured by Konica Minolta Co., Ltd. was used. The temperature of the inkjet head is set to 50 ° C. (however, only Example 26 is 80 ° C.), and the discharge condition is a condition that the droplet amount of one droplet is 42 pl, a resolution of 360 dpi × 360 dpi, and a recording speed of 500 mm / s. It was recorded in one pass under conditions.

  After the image was formed, the ink was cured by irradiating the image with ultraviolet light with an LED lamp (manufactured by Phoseon Technology, 395 nm, water-cooled LED) disposed in the downstream portion of the recording apparatus.

[Evaluation method]
The obtained images were evaluated for tape peeling resistance, flexibility, and abrasion resistance by the following methods. The results are shown in Tables 1-3.

(Adhesion (tape peeling resistance))
Cuts were made on the solid image printing portion based on a cross-cut tape peeling residue adhesion test (JIS K5400 cross-cut test), and an adhesive tape (Scotch # 250, manufactured by Sumitomo 3M) was attached. Then, after pressure-reciprocating once with a 2 kg roller, the adhesive tape was peeled off at once, and the adhesion of the coating film was evaluated from the number of the remaining coating films. Evaluation was performed according to the following criteria. Δ or more is a practically favorable range.

◎: Adhesion residual rate 90% or more and 100% or less ○: Adhesion residual rate 80% or more and less than 90% △: Adhesion residual rate 60% or more and less than 80% ×: Adhesion residual rate 60% or less

(Flexibility)
A solid image of 3 cm × 10 cm was printed, and the degree of curling due to curing shrinkage was visually observed and evaluated according to the following criteria. Note that Δ or more is a practically favorable range.
◎: Cured product is not warped ○: Cured product is almost not warped △: Cured product is warped, but within allowable range ×: Cured product is warped largely, NG level

(Abrasion resistance)
The above-mentioned solid image sample was rubbed 10 times on an unrecorded recording medium (OK top coat +, manufactured by Oji Paper Co., Ltd.) while applying a load with a paperweight (weight: 500 g). The recorded surface after rubbing was visually observed and evaluated according to the following evaluation criteria. Note that Δ or more is a practically favorable range.
◎: Image (coloring material) peeling on the recording surface was not visible ○: Image (coloring material) peeling on the recording surface was almost invisible △: Image (coloring material) peeling was slightly visible on the recording surface Although it was made, it was not at a level that would cause a problem in practice. ×: Image (coloring material) peeling on the recording surface was visually recognized in a considerable area.

  As shown in Tables 1-3, it contains a polyfunctional (meth) acrylate compound, a polyfunctional vinyl ether compound, and a fluorescent brightener, and the content of the polyfunctional (meth) acrylate compound is 60% by mass. In addition, in the case where the polyfunctional (meth) acrylate compound contains a hydrophobic (meth) acrylate compound, all of the adhesion (tape peeling resistance), flexibility, and abrasion resistance are good. Met. It is inferred that the optical brightener functions as a chain transfer agent and a chain transfer reaction has occurred during polymerization with the hydrophobic polyfunctional (meth) acrylate compound and the polyfunctional vinyl ether compound. However, when a part of the polyfunctional (meth) acrylate compound was not a hydrophobic polyfunctional (meth) acrylate compound (Example 7 and Example 24), the abrasion resistance tended to be low. It is inferred that the chain transfer reaction tended to be difficult to occur. Moreover, when the double bond which a polyfunctional vinyl ether type compound has is a double bond derived from a (meth) acryloyl group (Example 4), the case where it is a double bond derived from a vinyl ether group (Example 3) is more. The flexibility of the cured product was good. If the double bond of the polyfunctional vinyl ether compound is a double bond derived from a vinyl ether group, it is presumed that the crosslink density of the cured product is hardly increased excessively.

  On the other hand, when the amount of the polyfunctional (meth) acrylate compound is less than 60% by mass with respect to the total amount of the ink, the strength of the cured product is reduced, and the tape peeling resistance and the abrasion resistance are reduced (Comparative Example 1). . On the other hand, when the polyfunctional vinyl ether compound was not included, the flexibility was low (Comparative Examples 2 and 4). In this case, it is surmised that the crosslink density of the cured product has become excessively high. In addition, when no optical brightener was included, the abrasion resistance was not sufficient (Comparative Example 3). One possible reason is that the crosslink density of the cured product was low.

  According to the actinic ray curable ink-jet ink according to the present invention, a cured product having high flexibility, excellent adhesion to a recording medium, and good abrasion resistance can be formed. Therefore, the actinic radiation curable inkjet ink according to the present invention can be applied to various image formations such as package printing.

Claims (8)

A polyfunctional (meth) acrylate compound;
A polyfunctional vinyl ether compound,
An optical brightener;
Including
The content of the polyfunctional (meth) acrylate compound is 60% by mass or more,
The polyfunctional (meth) acrylate compound includes a hydrophobic polyfunctional (meth) acrylate compound,
Actinic ray curable inkjet ink. The polyfunctional vinyl ether compound is an ethylene oxide modified product,
The actinic ray curable inkjet ink according to claim 1. Further comprising an amine-modified (meth) acrylate oligomer,
The actinic ray curable inkjet ink according to claim 1. Further comprising a radical polymerization initiator,
The actinic-light curable inkjet ink as described in any one of Claims 1-3. The radical polymerization initiator includes an intramolecular bond cleavage type radical polymerization initiator,
The content of the intramolecular bond cleavage type radical polymerization initiator is 0.1 to 3.5% by mass,
The actinic ray curable inkjet ink according to claim 4. Further containing an antioxidant,
The actinic-light curable inkjet ink as described in any one of Claims 1-5. Further containing a coloring material,
The actinic-light curable inkjet ink as described in any one of Claims 1-6. At least one gelling agent selected from the group consisting of aliphatic ketones, aliphatic esters, higher fatty acids, higher alcohols, and amide compounds having a straight chain or branched hydrocarbon chain having 14 or more carbon atoms is 0.5 to Including 10% by weight,
The actinic-light curable inkjet ink as described in any one of Claims 1-7.